Core/Auras: Expanding functionality of SPELL_GROUP_STACK_RULE_EXCLUSIVE_SAME_EFFECT to be able to take care of aura effects inside their handlers

Currently handled:
- SPELL_AURA_MOD_RESISTANCE_PCT
- SPELL_AURA_MOD_STAT
- SPELL_AURA_MELEE_SLOW
- SPELL_AURA_MOD_MELEE_HASTE
- SPELL_AURA_MOD_DAMAGE_PERCENT_DONE

Necessary to allow stack rules such as BoK/BoS/Bok-Drums and others to be all in a target with all of the aura effects, yet with only the 'highest' effect active
Merge pull request #12233 from Trisjdc/aura_stacking

Core/Auras: Expanding functionality of SPELL_GROUP_STACK_RULE_EXCLUSIVE_SAME_EFFECT to be able to take care of aura effects inside their handlers
Core/Auras: Correct a typo that caused bad stacking of SPELL_AURA_MOD_MELEE_HASTE
Core/PetAI: Fix memory leak

Fix memory leak added in e7f0808d467210c2e0ca455cf810e52700518849

Valgrind log:
395,712 (390,216 direct, 5,496 indirect) bytes in 229 blocks are definitely lost in loss record 65 of 67
 at operator new(unsigned long) (vg_replace_malloc.c:320)
 by PetAI::UpdateAI(unsigned int) (PetAI.cpp:167)
 by Creature::Update(unsigned int) (Creature.cpp:541)
 by TempSummon::Update(unsigned int) (TemporarySummon.cpp:47)
Merge branch 'master' of https://github.com/TrinityCore/TrinityCore